1. Field of the Invention
The present invention relates to the field of devices for filtering electromagnetic interference, and more particularly to a novel electromagnetic interference filter, which may be placed about the exterior of an electrical signal-carrying cord or cable so that a ferrite core is in position to absorb extraneous radio frequency electromagnetic noise waves usually present on all cables and electrical conductors.
2. Brief Description of the Prior Art
Filtering of electromagnetic interference has become a major area of concern in the transmission, reception and processing of electronic signals. Various domestic and international regulating agencies have provided limitations on interference emission levels to which producers of electronics hardware must adhere. The use of soft ferrites in the reduction of conducted interference has become an important strategy in meeting these requirements.
The application of ferrite components to reduce conducted electromagnetic interference has become more and more prevalent with faster clock speeds in today's data processing systems and with tighter mandated regulations on emission standards. The use of ferrites is effective in this application for many reasons, but their utility is derived primarily from their magnetic and dielectric frequency response characteristics.
Although ferrite compositions and materials have been known, difficulties and problems have been encountered when it was desired to mount the ferrite component into a circuit or in an effective position to achieve the filtering function. In some instances, attempts have been made to apply a ferrite component directly onto a signal-transmitting cable with the result that the ferrite material or composition would not be in the generated pattern or direction of extraneous radio frequency so as to absorb such interference accompanying an intelligence signal carried by the cable. Such problems stem largely from the fact that the ferrite component may slide or become easily dislodged from its installed position, and in other instances, it is difficult to apply the ferrite component onto a cable or electrical conductor so that it will not interfere with conductor or cable installation. Most prior applications require that the ferrite component be added during the manufacture of the cable so that once the cable has been installed, modification cannot readily be made to include the ferrite component on the cable. Of major importance is the need to install a magnetic ferrite component so that it is in proper magnetic flux directional polarity so that a harmonizing orientation is produced.
Therefore, a long-standing need has existed to provide a novel electromagnetic interference filter which employs magnetic ferrite material that can be readily installed on an existing cable and in proper magnetic flux directional orientation position for absorbing, filtering or collecting extraneous radio frequency electromagnetic waves or the like. Such a filter should include means for retaining the filter in its installed position and should provide means for clamping or fixedly securing the filter onto the cable at the critical location.